Saturable variable inductor



Mal'Ch 11, 1958 A. NEWTON 2,826,748

* SATURABLE VARIABLE INDUCTOR Filed Marcia 26, 195e IIIIl..

contribute materially to 2,826,748 STURABLE VARIABLE INDUCTORV Arnoldv Newton, Forest Hills, N. Y'.,y assignor tor F-R Machine Works, Inc., Woodside, N; Y., a corporation of New York i Y Application March 26, 1956, ScrialfNot` 573,889 7A Claims. (Cli 33o- 155) Thepres'ent invention relates to saturable variable inductorsiand. moreespe'cially to such inductors whereinthe inductancemangeis substantially increased, thus rendering` Variablesaturablei inductance varrangementsA :are knownin theprior art but up'Y to the-presenti thecontrollthereof has resided.- exclusively in' the direct utilizationr of the variable permeability phenomenon ofy certain magnetic materials upon=.inductance, when said materials are subjected to a-saturatin'g magnetic eld. Themaximum inductance'range. attainable with. the conventional arrangement islrestricted to the ratio of inductance of the coil incorporating vthe saturable magnetic material in'its core vvhenthev material exhibitsmaximum permeability to the inductancelof the same coil, when the permeability,- of.the=

magneticvmaterial is. reduced to unity, a condition-prevailing Whenlthemagneticmaterial is fully saturated. by a .magnetic field. Ini contradistinction, the present invention enablesl a-'iurther reduction of'inductance uponsaturation, thereby increasing the range, by theutilization. of acombination ofy materials having. predetermined properties;

yFor example, certain high permeability materialshave the ability to increase the: inductance ofl a coiland to provide magnetic shielding by concentrating magnetic yux ini the magnetic materialwhile at the same time such magnetic material is susceptible to permeability control by means of aV magnetic field.

The :introduction `of a nonmagnetic conductive material Withthemagnetic, material interposed betwcenlit andi the coil, oftwhichithis combinationforms the.l core, will-exert little-effect uponthe inductance ofthe coilv when the permeability. is. high becausev or ther shielding etect of the? magnetic material, while at the same time. will also the reduction ofinductance upon saturation as a result of coupling .to the'- coil-ofthev conductive element of the core.

lt, isl emphasized that the function of the conductive element is distinct from that of a shield, which is generally incorporated between the'signal and control elements of the device. The shield is employed for the sole. purpose of reducing losses and maintaining high Q, byfminimizing coupling to the yoke and/or thefcontrol winding which may be subject to loss at frequencies associated with the voltage in thesignal winding. Nevertheless,the conductive element of thepresentinvention maybe sofarrangedasto.provide shielding in additionwto its.-y primary function. of extendingthe inductan'cerange. The shielding action, however, is incidentalandl is notlthe subject matterof any patent claims.`

It: isr accordingly the primary object of theV presentinvention'` to Iprovide a saturable variable .inductor in Vwhich a saturable magnetic material .is employed, in combination with acond-uctive medium soarranged as to take advantage of the high relative permeabilityof the magnetic 2,826,748 Patented Mar. 11, 1958 material in the" absence of a saturating magneticv eld, while at the-same time allowing the conductive medium to reduce the inductance by'virtue of its coupling effect when a magnetic eldis applied and saturation is appreached;

lStillf-urth/er" objects'of the present invention will become obvious to those skilledlin the art by reference to the accompanying drawing, wherein:

Figure l isa-.schematic illustrationof aworkingrmodel whereint afsaturableA variableinductor of the present invention` is fused,

Fig. 2'1is la'sectionalviewv of the saturable element placed inthe gapfasfshownfinFig, l,

Fig. Bis a-.sectionalv-view taken on-the line III-llIof Fig-.V4 is.a1viewsimilar to that'of- Fig. 2 but showingA a slightly different modification which the present invention mayr take,

Fig. 5 is also a sectional view of another modification which the-present invention'may take,

Eig.- 6 is another sectional view which a stillfurther moditication. of= the presentA invention mayl take,

Fig.` 7 is a1 sectional. plan. View takenv on thev line VII- VIIl of Fig. .6;

Fig.y 8v is' a: graphic illustration showing theoperating characteristicsot a saturable variable inductor constructed in accordance` with the`v present invention compared with inductors of'theprior: a'rt and inl which thelabscissar'epresents electromagnetA currentv in'd milliamperes and the ordinaterepresents` tuned frequency' in. megacycles, and

Fig.y 9i shows'.` a toroidal congurationi embodying the principles of: the: present invention 1 Wherein'i thef corelv of the toroidal ri'ng contains' the' nonmagneticy conductive substance while the saturable magnetic'materialformsthe outside surface.v

Referring now to` the'drawing inidetail, the working modelfwherenthe present invention-Was t'estedf is shown inFig.' l. It comprises' a saturating.' reactor yoke-5: of magnetic material,.suchasirotnora` suitable alloy, having. ay gapV n'tits core and` providedr with ain Velectroma'gn'et control winding 6 surrounding a portion ofV this` yoke,

.Positioned-in the4 gap ofl they yoke Sfisia tube-7 of high yforms-parteithefsignalf circuit` inv operation of the inductorgis woundiab'outrthetube 7 ofisaturablematerial andsuitable'shields 10mi-a1 metallic foil, suchas` silver, copper, orthe like; may beinterposedhetweenlthe ends of the tubef7 and theadjacentends' ofithe' reactor yoke 5 for the sole purpose of minimizing coupling between windingf9 and yokez 'andforwinding 6 :thereby reducing circuit' losses: and maintaining high Q,- asis well' known in the'art.

The inductance'- of".y the. c'oil 9, normallyy included in the signal? circuit, willinh'eren'tly be increasedin aiwell known manner by:` the'insertion ofv af'highvpermeability coresuchiastheferrite-'tubef 7, inv itsttield.- However, the inductance of 1 such' coil 9 will? b'e materially reduced if, instead-"offy the'. highpermeability core representedv by thetube 7,' a-highf conductivity'v n'o'nmagnetielf material, suchas-aftube^1orv rod/.of silver,.copp'ei" or the like 8,' is introducedA in'itsr field.' Byssurrounding this tube of electricallyl conductivevnonmagn'etic matera1= S-with al high .permeabilityf magnetic-rmaterial such as the; ferrite tube -7, the inductancer oft the* c'oil 9' is again increased and the coupling eect.ofhtheconductive tube or -rodS'is-rninirnizedk because.x ofi the: higher" concentration' of magnetic ilux*in1the.'magneticmaterial 7i This=magnetic tubeV 7 thus`r acts asy a magnetic-shield reducing the coupling bcvrfavorable operating apparent from Fig. 8.

tween the coil 9 and the conductive tube or rod'S. Saturation of the magnetic member will reduce the permeability to unity making it equivalent to the withdrawal of the magnetic material 7 from the field of coil 9, with attendant reduction of its inductance in the signal circuit due to coupling of coil 9 to conductive member 8.

The change in the inductance range is determined by the ratio of the inductance of formed of a high permeability material and the inductance of this same coil when the magnetic core is replaced by a nonmagnetic conductive material. By reference to Fig. 8 it will be readily seen from curve A, representing oscillator frequency when coil 9 was connected in a Y placing the nonmagnetic conductive material 18 on the ex- Y terior, as shown in Fig. 4, or two coaxial tubes 17 and and having nonmagnetic exterior surfaces 38, which structure is considered capable of high efliciency and range.

A still further increase in efciency is attainable through point on the magnetization curve where a reduction of hysteresis etlects results at the same Y time.

The increased range at higher relative ux densities is It frequently happened that cerposite core in accordance with the present invention, by affording increased range at higher llux levels.

such inductors and wherein improved high-frequency performance is achieved together with a reduction Yin hyslar arrangement of the controlling element. A permanent 4magnet arrangement may, for instance, be employed to coil 9` when the core is -provided with an air-gap 30 -eld in the air-gap of said yoke by variation of thc current through the air-gap of said yoke, a high permeability saturable .magnetic member concentrically disposed relative to said inductance range of said saturable Vcurrent through -in the air-gap of said yoke, a high permeability saturable magnetic member concentrically disposed relative to said -ing being induced in said minimizing circuit losses,

Ysignal winding high permeability of increasing the overall inductance aeaams appended claims.

I claim:

l. A saturable inductor comprising a yoke of magnetic material having an air-gap therein, a control winding surrounding said yoke, a composite core having a saturable ferromagnetic member disposed in the air-gap of said yoke, a coil in close proximity to said ferromagnetic member, and a nonmagnetic electrically conductive member separated from the coil by the interposition of said magnetic member, said nonmagnetic electrically conductive member being essentially shielded from said coil when the permeability of said juxtapositioned saturable ferromagnetic member is high and said nonmagnetic electrically conductive member being coupled to said coil when saturation is approached, thus reducing the inductance and extendingthe range of said inductor.

2. A saturable variable inductor of increased inductance range comprising a yoke of magnetic material therein, a control coil wound about a portion of said yoke for controlling the magnetic said coil, a signal winding disposed in signal winding and in said air-gap for increasing the linductance or" said signal winding, and a nonmagnetic electrically conductive material concentric with said -signal winding but separated permeability saturable magnetic from it by said high member for reducing the inductance of said signal winding when a magnetic field is applied to said high permeability saturable magnetic member by flow of control current through said control coil and saturation of said magnetic member is approached, for the purpose of increasing the overall variable inductor.

, 3. A saturable variable inductor of increased inductance range comprising a yoke of magnetic material provided with an air-gap therein, a control coil wound about a portion of said yoke for controlling the magnetic field in the air-gap of said yoke by variation of thc said coil, a signal winding disposed signal windingin said air-gap for increasing the inductvance of said signal winding, metallic nonmagnetic shields 'disposed in said air-gap between the ends of said yoke and the ends of said high permeability saturable magnetic member to prevent the signal from said signal windcontrol coil or yoke and thus and a nonmagnetic electrically conductive material concentric with said signal winding but separated from it by said high permeability saturable magnetic member for reducing the inductance of said when a magnetic field is applied to said saturable magnetic member by ow of control current through said control coil and saturation of said magnetic member is approached, for the purpose range of said saturable variable inductor.

4. A saturable variable inductor of increased inductance range comprising a yoke of magnetic material provided with an air-gap therein, a control coil wound about a portion of said yoke for controlling the magnetic eld in the air-gap o-f said yoke by variation of the current through said coil, a signal winding disposed in the air'- gap of said yoke, a high permeability saturable magnetic tubular member disposed interiorly of said winding and supporting the same for increasing the inductance of said signal winding, and a layer of nonrnagnetio electrically conductive material on the interior surface of said magnetic tubular member for reducing the inductance of said signal winding when a magnetic ieid is applied to said high permeability saturable magnetic tubular member by flow of control current through said control coil and saturation of said magnetic tubular member is approached, for the purpose of increasing the overall inductance range of said saturable variable inductor.

5. A saturable variable inductor of increased inductance range comprising a yoke of magnetic material provided with an air-gap therein, a control coil wound about a portion of said yoke for controlling the magnetic field in the air-gap of said yoke by variation of the current through said coil, a signal Winding disposed in the air-gap of said yoke, a high permeability saturable magnetic tubular member disposed about said winding and supported by the latter for increasing the inductance of said signal winding, and a nonmagnetic electrically conductive material on the exterior surface of said magnetic tubular member for reducing the inductance of said signal winding when a magnetic field is applied to said high permeability saturable magnetic tubular member by iiow of control current through said control coil and saturation of said magnetic tubular member is approached, for the purpose of increasing the overall inductance range of said saturable variable inductor.

6. A saturable variable inductor of increased inductance range comprising a yoke of magnetic material provided with an air-gap therein, a control coil wound about a portion of said yoke for controlling the magnetic field in the air-gap of said yoke by variation of the current through said coil, a signal winding disposed in the air-gap of said yoke, a pair of concentric high permeability saturable magnetic tubular members concentric With said signal winding, one of said tubular members being inside said windingand supporting the same and the other of said tubular members surrounding said winding and inner tubular member, for increasing the inductance of said signal winding, and a nonmagnetic electrically conductive material covering the interior surface of said inner magnetic tubular member and the exterior surface of said outer magnetic tubular member for reducing the inductance of said signal winding when a magnetic field is applied to said high permeability concentric saturable magnetic tubular members by fiow of control current through said control coil and saturation of said magnetic tubular members is approached, for the purpose of increasing the overall inductance range of said saturable variable inductor.

7. A composite core for a saturable variable inductor comprising a iat spirally wound signal winding, a pair of high permeability saturable magnetic disc-like members disposed on each side of said at spiral winding for increasing the inductance of said signal winding, and a thin disc-like nonmagnetic electrically conductive material covering said magnetic disc-like members on the side of each opposite to that adjacent said flat spiral winding for reducing the inductance or' said signal winding when a magnetic field is applied to said disc-like magnetic members and saturation of said disc-like magnetic members is approached, for increasing the overall inductance range of the saturable variable inductor employing said composite core.

References Cited in the file of this patent UNITED STATES PATENTS 2,361,542 Gumleyv Oct. 3l, 1944 2,628,342 Taylor Feb. 10, 1953 2,633,561 Hewlett Mar. 3l, 1953 OTHER REFERENCES 

